Waferizing apparatus, that is apparatus to produce wafers from logs for use in the production of wafer board, are extremely well known. They resemble wood chippers in appearance but differ in the product they are designed to produce. Chippers cut wood across the grain to produce chips for the production of wood pulp. Waferizers cut the wood substantially parallel to the grain to produce wafers or flakes for the manufacture of waferboard and its derivatives.
In the past, waferizing apparatus has generally comprised a large rotating cutting disc or drum mounted on a driven shaft. The disc or drum has openings formed in it. On one surface is mounted a carrier for the waferizing knives which are disposed in the openings of the passageways. The knives are held in position by clamps contacting the planar surface of the knives. Clamps are usually held in place by bolting through into a threaded insert located within a recess in the carrier, on the surface of the carrier remote from the clamps. The knife typically has a counter knife disposed beneath it, that is against the carrier, and the knife and counter knife are bolted in position. Applicant's U.S. Pat. No. 4,685,497 is indicative of the prior art for its showing of a conventional arrangement of a rotary cutting disc.
While variations of this rotary cutter occur, prior art chipping or waferizing apparatus relies almost exclusively on an arrangement wherein the rotating cutting disc or drum is mounted to an immovable base and logs are advanced into the rotating cutting blade at an appropriate orientation. As the disc or drum rotates the knives, which project from the outer surface of the cutting element beyond the clamps and the carrier, cut through the logs pressed against the carrier. Examples of such prior art devices include U.S. Pat. No. 3,346,027 to Kirsten in which logs are advanced against a rotating disc having cutting knives by a feed system comprising a hydraulic ram operating within a feed trough. U.S. Pat. No. 4,681,146 to Liska teaches a method and apparatus for producing wood flakes using a rotating disc with cutting blades to process logs advanced and held against the disc by an infeed conveyor system. U.S. Pat. No. 4,161,972 to Hanaya discloses a further variation of this arrangement wherein logs to be processed are advanced against a rotating cutting disc.
The standard arrangement of the prior art has a major disadvantage in that it can be difficult to accurately control the advance of the logs into the rotating disc or drum with the result that chips or wafers of variable quality are produced. Logs for processing can be highly variable in shape and size and moving a collection of such logs at a controlled and predictable rate can be difficult and labour intensive. Also, as the cut must be made parallel with the wood grain, the logs must be introduced with their longitudinal axis at right angles to the axis of rotation of the cutting disc or drum. The logs therefore have to be cut to a pre-determined length which causes problems associated with fiber loss through saw kerfs and short log ends, handling problems, and increased capital and maintenance costs for conveyors and slasher decks to transport the cut logs.